1. Field of the Invention
The present invention relates to a valve operating system in an internal combustion engine, including a swinging support section provided at a base end of a rocker arm and swingably carried on a rocker shaft mounted in a cylinder head, a plurality of valve abutments provided at a tip end of the rocker arm and capable of being individually put into abutment against upper ends of a plurality of engine valves, and a cam abutment provided on the rocker arm in an intermediate portion between the swinging support section and each of the valve abutments to come into contact with a valve operating cam.
2. Description of the Related Art
Such a valve operating system is conventionally known, for example, from Japanese Patent Application Laid-open No. 6-185322.
In a valve operating system constructed such that a plurality of engine valves are driven by a single rocker arm, a difference in tappet clearance may be produced between the plurality of engine valves and a plurality of valve abutments provided on the rocker arm in individual correspondence to the engine valves due to the lapse of an operating time. If such a difference in tappet clearance is produced, a force causing the rocker arm to be inclined is applied to the rocker arm by a large load generated on a line interconnecting the cam abutment and one of the valve abutments at one end of an array of the valve abutments. For this reason, a large load is applied to opposite ends of the swinging support section in an axial direction of the rocker shaft, and if the swinging support section does not have a rigidity enough to withstand such load, there is a possibility that uneven wear may be produced in the swinging support section, resulting in a reduction in durability of the swinging support section. In the rocker arm of the above known valve operating system, however, the swinging support section is formed into a cylindrical shape at a wall thickness uniform over the entire length in the axial direction of the rocker shaft, and if the wall thickness of the swinging support section is increased in order to enhance the rigidity of the swinging support section, the weight of the rocker arm is increased.
Accordingly, it is an object of the present invention to provide a valve operating system in an internal combustion engine, wherein the durability of the rocker arm is enhanced, while avoiding an increase in weight of the rocker arm.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a valve operating system in an internal combustion engine, including a cylindrical swinging support section provided at a base end of a rocker arm and swingably carried on a rocker shaft mounted in a cylinder head, a plurality of valve abutments provided at a tip end of the rocker arm and capable of being individually put into abutment against upper ends of a plurality of engine valves, and a cam abutment provided on the rocker arm in an intermediate portion between the swinging support section and each of the valve abutments to come into contact with a valve operating cam, wherein the swinging support section includes a thinner cylindrical portion surrounding the rocker shaft, and thicker cylindrical portions which are form ed at a thickness larger than that of the thinner cylindrical portion into a cylindrical shape to surround the rocker shaft and which are integrally and continuously provided at axially opposite ends of the thinner cylindrical portion, respectively.
With such arrangement of the first feature, a central portion of the swinging support section can be formed at a smaller thickness, thereby avoiding an increase in weight of the rocker arm, while the opposite end portions of the swinging support section, to which a large load may be possibly applied, can be formed at a larger thickness, thereby enhancing the rigidity of supporting of the rocker arm to enhance the durability of th e rocker arm.
According to a second aspect and feature of the present invention, in addition to the first feature, the swinging support section has grooves defined in its inner surface at opposite ends thereof along the axis of the rocker shaft and capable of accumulating an oil between the opposite ends and an outer surface of the rocker shaft, respectively.
With such arrangement of the second feature, the oil can be accumulated between the opposite ends of the swinging support section and the rocker shaft, and even if the rocker arm is inclined, the generation of uneven wear can be prevented to the utmost, thereby enhancing the durability of the rocker arm. Moreover, the grooves are merely provided in the inner surface of the swinging support section at its opposite ends and hence, the weight of the rocker arm cannot be increased.
According to a third aspect and feature of the present invention, in addition to the second feature, first one of the valve abutments arranged in parallel to the axis of the rocker shaft, which is disposed on one side along the axis of the rocker shaft, is provided at a tip end of a first support wall provided to extend from one end of the swinging support section at a location corresponding to one of the grooves, and second one of the valve abutments, which is disposed on the other side along the axis of the rocker shaft, is provided at a tip end of a second support wall provided to extend from the other end of the swinging support section at a location corresponding to the other groove.
With such arrangement of the third feature, a reduction in rigidity of the opposite ends of the swinging support section due to the provision of the grooves can be made up for by the support walls.
According to a fourth aspect and feature of the present invention, in addition to the first feature, the swinging support section includes a thinner cylindrical portion surrounding the rocker shaft, and thicker cylindrical portions which are formed at a thickness larger than that of the thinner cylindrical portion into a cylindrical shape to surround the rocker shaft and which are integrally and continuously provided at axially opposite ends of the thinner cylindrical portion, the thicker cylindrical portions having grooves provided in their inner surfaces respectively and capable of accumulating an oil between the inner surfaces and an outer surface of the rocker shaft.
With such arrangement of the fourth feature, a central portion of the swinging support section can be formed at a smaller thickness, thereby avoiding an increase in weight of the rocker arm, while the opposite end portions of the swinging support section, to which a large load may be possibly applied, can be formed at a larger thickness, thereby enhancing the rigidity of supporting of the rocker arm. Further, the oil can be accumulated between the opposite ends of the swinging support section and the rocker shaft and hence, the generation of uneven wear can be prevented to the utmost. Moreover, since the grooves are provided in the inner surface of the thicker cylindrical portion, it is possible to avoid a reduction in rigidity of the swinging support section due to the provision of the grooves and to reliably enhance the durability.
According to a fifth aspect and feature of the present invention, in addition to the first feature, a pair of intersection points, at which the following straight lines and the axis of the rocker shaft intersect one another, are disposed at locations inner than the axially opposite ends of the swinging support section: a first straight line passing through (1) a center of first one of the valve abutments arranged in parallel to the axis of the rocker shaft, which is disposed at one end along the axis of the rocker shaft, and (2) an area of contact of the valve operating cam with the cam abutment; and a second straight line passing through (1) a center of second one of the valve abutments, which is disposed at the other end along the axis of the rocker shaft and (2) the area of contact of the valve operating cam with the cam abutment.
With such arrangement of the fifth feature, a difference in tappet clearance is produced between the first and second ones of the valve abutments arranged in parallel to the axis of the rocker shaft, which are disposed at the one end and the other end along the axis of the rocker shaft. Even if a large load is generated on the first or second straight lines and acts to incline the rocker arm, the rocker arm can be supported stably and prevented from being inclined, because, the swinging support section is supported on the rocker shaft on the first and second straight lines. Therefore, it is possible to prevent the generation of uneven wear in the swinging support section and the cam abutment.
According to a sixth aspect and feature of the present invention, in addition to the fifth feature, the swinging support section is formed at a length larger than a distance between the first and second abutments, and straight lines passing through centers of the first and second valve abutments and perpendicular to the axis of the rocker shaft are disposed at locations inner than the axially opposite ends of the swinging support section. With such arrangement of the sixth feature, the swinging support section is supported on the rocker shaft over a length larger than the distance between the valve abutments at the one end and the other end along the axis of the rocker shaft, and the rocker shaft can be supported more stably.
According to a seventh aspect and feature of the present invention, in addition to the first feature, the swinging support section has a rib projectingly provided on an outer surface thereof to extend in a direction intersecting a plane perpendicular to the axis of the rocker shaft. With such arrangement of the seventh feature, the rib is projectingly provided on the outer surface of the swinging support section to extend in the direction intersecting the plane perpendicular to the axis of the rocker shaft. Therefore, as compared with a system in which the entire swinging support section is formed at a larger thickness, it is possible to avoid, to the utmost, that the layout of the rocker arm is limited, and to enhance the rigidity of the swinging support section, while suppressing an increase in weight of the rocker arm to the minimum.
According to an eighth aspect and feature of the present invention, in addition to the seventh feature, the rib is provided on an outer surface of the thinner cylindrical portion to connect the thicker cylindrical portions to each other. With such arrangement of the eighth feature, it is possible to further enhance the rigidity of the swinging support section to provide an increase in durability by interconnecting the thicker cylindrical portions at the opposite ends of the swinging support section, to which a large load may be possibly applied.
According to a ninth aspect and feature of the present invention, in addition to the seventh or eighth feature, the rib is formed to protrude from the swinging support section in a direction intersecting a plane perpendicular to a direction of application of a load from the valve operating cam to the rocker arm. With such arrangement of the ninth feature, it is possible to sufficiently enhance the rigidity of the swinging support section against a strike load from the valve operating cam.
According to a tenth aspect and feature of the present invention, in addition to the seventh or eighth feature, a pair of the ribs are provided on the outer surface of the swinging support section at locations symmetric with the axis of the rocker shaft. With such arrangement of the tenth feature, it is possible to enhance the rigidity of the swinging support section by an extremely small number of the ribs and to suppress an increase in weight of the swinging support section and thus the rocker arm to the minimum.
According to an eleventh aspect and feature of the present invention, in addition to the seventh or eighth feature, the cylinder head having the rocker shaft mounted therein has a mounting member mounted therein and disposed sideways of the swinging support section, and the swinging support section has a notch provided therein at a location corresponding to the mounting member and recessed on a side opposite to the mounting member. With such arrangement of the eleventh feature, the rocker arm can be disposed in proximity to the mounting member, while maintaining a rigidity increasing effect provided by the rib, and the limitation of the layout of the rocker arm can be further moderated. In addition, the weight of the rocker arm can be reduced by the provision of the notch and moreover, a reduction in rigidity due to the provision of the notch can be inhibited by the rib.
According to a twelfth aspect and feature of the present invention, there is provided a valve operating system in an internal combustion engine, comprising a cylindrical swinging support section provided at a base end of a rocker arm and swingably carried on a rocker shaft mounted in a cylinder head, a plurality of valve abutments provided at a tip end of the rocker arm and capable of being individually put into abutment against upper ends of a plurality of engine valves, and a cam abutment provided on the rocker arm in an intermediate portion between the swinging support section and each of the valve abutments to come into contact with a valve operating cam, wherein the swinging support section has grooves provided in its inner surface at opposite ends thereof along the axis of the rocker shaft and capable of accumulating an oil between the opposite ends and an outer surface of the rocker shaft.
With such arrangement of the twelfth feature, the oil can be accumulated between the opposite ends of the swinging support section and the rocker shaft, and even if the rocker arm is inclined, uneven wear can be prevented to the utmost from being produced in the rocker arm. Moreover, the grooves are merely provided in the inner surface of the swinging support section at the opposite ends thereof and hence, the weight of the rocker arm cannot be increased.
According to a thirteenth aspect and feature of the present invention, there is provided a valve operating system in an internal combustion engine, comprising a cylindrical swinging support section provided at a base end of a rocker arm and swingably carried on a rocker shaft mounted in a cylinder head, a plurality of valve abutments provided at a tip end of the rocker arm and capable of being individually put into abutment against upper ends of a plurality of engine valves, and a cam abutment provided on the rocker arm in an intermediate portion between the swinging support section and each of the valve abutments to come into contact with a valve operating cam, wherein the swinging support section comprises a thinner cylindrical portion surrounding the rocker shaft, and thicker cylindrical portions which are formed at a thickness larger than that of the thinner cylindrical portion into a cylindrical shape to surround the rocker shaft and which are integrally and continuously provided at axially opposite ends of the thinner cylindrical portion, respectively, the thicker cylindrical portions having grooves provided in their inner surfaces, respectively, and capable of accumulating an oil between the opposite ends and an outer surface of the rocker shaft.
With such arrangement of the thirteenth feature, a central portion of the swinging support section can be formed at a smaller thickness, thereby avoiding an increase in weight of the rocker arm, while the opposite end portions of the swinging support section, to which a large load may be possibly applied, can be formed at a larger thickness, thereby enhancing the rigidity of supporting of the rocker arm. The oil can be accumulated between the opposite ends of the swinging support section and the rocker shaft, and even if the rocker arm is inclined, uneven wear can be prevented to the utmost from being produced in the rocker arm. Moreover, the grooves are provided in the inner surfaces of the thicker cylindrical portions and hence, it is possible to avoid a reduction in rigidity of the swinging support section due to the groove and to reliably enhance the durability of the swinging support section.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.